Container ships with upper structures for loading and unloading cargo containers are disclosed in U.S. Pat. Nos. 4,043,285 to Nordstrom, U.S. Pat. No. 4,294,185 to Nordstrom et al, and U.S. Pat. No. 5,183,305 to Nordstrom et al, the subject matter of each of which is hereby incorporated by reference. These ships maximize cargo carrier capacity, minimize idle port time and provide a highly efficient system for loading and unloading the cargo. Automated cranes on ships guarantee fast turn around in ports saving manpower and time, particularly reducing or eliminating the need for manual labor in the ships' holds for loading and unloading the cargo. Additionally, large amounts of cargo can be stored in a secure manner in a minimum amount of time and with minimum labor requirements. Further, the loading and unloading operations can be carried out even in bad weather or high winds.
Although these Nordstrom container systems are highly effective for cargo that is not temperature sensitive, they have not been adapted for handling refrigerated cargo. Certain food cargo products must be maintained in a refrigerated state during transit to avoid damage or spoilage.
Conventional refrigerated ships intended for transporting breakbulk or palletized cargo have holds divided by decks two to three meters high, providing spaces with perforated deck grating. These spaces form air ducts under the cargo. Refrigerated air is blown into the ducts at the end of the hold or through side ducts. The refrigerated air ascends through the cargo and through the duct at the opposite end of the hold, and then returns to the refrigeration unit via spaces above the cargo. Two of these between deck spaces can be combined to form a common air space, although such combination risks incomplete refrigeration at the higher levels of the hold.
The loading and the unload of the cargo in these conventional refrigeration systems for cargo ships can be performed with onboard cranes and booms. Horizontal transport inside the hold and tight storing of the cargo to prevent shifting is accomplished with forklift trucks.
Another refrigeration system for container ships involves using refrigerated containers, each of which has its own independent refrigeration unit or machinery. These units can be used in any container ship as long as adequate electrical power from the ship is provided to each container for running its refrigeration unit. However, adequate ventilation must be provided in the cargo hold to dissipate the heat emitted by the refrigerated units. These independently refrigerated containers can be loaded using cranes, trailers, cassettes, forklift trucks and straddle carriers.
Some container ships have refrigeration units which supply refrigerated air through ducts. These ducts are coupled to containers which are thermally insulated. Suitable couplings are provided on the containers for conveying the inlet air into and exhaust air from the insulated containers.
Special ships for palletized cargo use a warehouse--type storage system. The pallets are loaded with a ship board stacker crane from the side of the ship, and are transported to special pallet rows. Refrigerated air is conveyed to these rows through ducts.
These conventional ship refrigeration systems have a number of problems. The systems are not adaptable to wide variety of different arrangements, without structural modification. Additionally, they are expensive and inefficient in the use of the particular containers and in the loading and unloading of the containers within the ships.